Report on Kilauea (United States) — 3 August-9 August 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 August-9 August 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Kilauea (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 August-9 August 2011. Smithsonian Institution and US Geological Survey.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
HVO reported that on 3 August at 1402 the floor of Kilauea's Pu'u 'O'o crater, which had risen significantly over the past month, began to subside. At 1420 lava erupted from a vent low on the W flank of the Pu'u 'O'o cone, about halfway between Pu'u 'O'o Crater and the E end of the Kamoamoa fissure, and formed two branches. The weaker flow traveled N into a forested kipuka. The higher-volume S branch quickly advanced down Kilauea's S flank along the edge of flows erupted during 2002-2004. By 1515, the crater floor and perched lava lake began to collapse; the circulation in the lava lake was maintained as the crater floor dropped. Within a few hours the lava lake was no longer visible and the crater floor, which had dropped 75-85 m, was covered with rubble. Between 1530 and 1615, the preliminary sulfur dioxide emission rate from all east rift zone sources was as high as 7,000 tonnes/day. The rate decreased to 4,000 tonnes/day at about 1700. Also by that time the lava flow had advanced 3.6 km.
During 4-9 August lava continued to flow from multiple W-flank vents topped with spatter cones, ponding in a low area due to a decreasing effusion rate. The Pu'u 'O'o crater rim was extremely unstable; continued collapses along the crater walls sent blocks of rock onto the crater floor. Lava also slowly flowed back onto the collapsed crater floor.
During 3-9 August the level of the summit lava lake fluctuated deep in the 150-m-diameter vent inset within the E wall of Halema'uma'u Crater and circulated with various patterns. Overall, the lake level receded and on 6 August was about 75 m below the crater floor. Periodic measurements indicated that the gas plume from the vent continued to deposit variable amounts of ash and occasionally fresh spatter nearby.
Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.